Refund was LESS than what I was charged?!

I bought a reciprocating saw online and it was supposed to come with a free battery as part of a promotion. The only reason I bought that particular saw was for the battery. They ended up cancelling the battery because they were out of stock. Because of that, I called and cancelled my order completely.

I checked my email and the refunded amount was $100 LESS than what I was charged.

Is it possible the refund for the battery will be separate? Any insight would be appreciated.

I’m going to give it a few days to see if the refund gets posted properly before I go nuclear on Customer Service.